Abstract: In order to suppress the input current harmonics and output voltage ripple of the 12-pulse rectifier further, this paper proposed a 24-pulse rectifier with an auxiliary single-phase rectifier (ASR) in series at DC side. The proposed 24-pulse rectifier was composed of a conventional 12-pulse rectifier, an interphase reactor with a secondary winding and ASR. The output of ASR was connected in series in the load path to modulate the output current of the rectifier bridge directly to increase the output current state of the rectifier, and then doubled the number of input current steps of the rectifier. The average value of the output voltage of the two rectifier bridges was superimposed with the output voltage of the ASR, and the output voltage pulses were doubled from 12 to 24. This method only needed a small-capacity ASR (only 2% of the output power) to increase the pulse number of the rectifier from 12 to 24, which reduced input current harmonics and output voltage ripple effectively. It also had advantages such as simple circuit structure, good symmetry, easy implementation and high reliability. An experimental prototype with an output power of 1.2kW was built to verify the correctness and effectiveness of the proposed method.